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TB Infection Control: Principles, Pitfalls, and Priorities

TB Infection Control: Principles, Pitfalls, and Priorities. Kevin P. Fennelly, MD, MPH Interim Director Division of Pulmonary & Critical Care Medicine Center for Emerging & Re-emerging Pathogens UMDNJ-New Jersey Medical School fennelkp@umdnj.edu. Objectives.

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TB Infection Control: Principles, Pitfalls, and Priorities

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  1. TB Infection Control:Principles, Pitfalls, and Priorities Kevin P. Fennelly, MD, MPH Interim Director Division of Pulmonary & Critical Care Medicine Center for Emerging & Re-emerging Pathogens UMDNJ-New Jersey Medical School fennelkp@umdnj.edu

  2. Objectives • To review basic principles underlying TB transmission and TB Infection Control policies. • To review the recent history of TB Infection Control. 3. To discuss personal observations and offer practical solutions to common problems in TB Infection Control.

  3. Is TB an Occupational Disease of HCWs? - Menzies D et al. IJTLD 2007; 11:593

  4. HCW Deaths due to Nosocomial Transmission of DR-TB • MDR outbreaks U.S. 1980s-1990s • 9 HCWs died • All immunocompromised, 8 with HIV • Sepkowitz KA, EID 2005 • XDR-TB outbreak, So Africa, 2006 • 52/53 died of unrecognized XDR-TB • 44/44 tested were HIV+ • Median survival from sputa collection=16 days • 2 HCWs died; 4 others sought care elsewhere • Gandhi N, Lancet 2006

  5. Personal Respiratory Protection Against M. tuberculosis: Contentious Controversy

  6. from Sol Permutt, 2004

  7. Wells-Riley Equation: Mathematical model of airborne infection Pr{infection}=C/S=1-e(-Iqpt/Q) Where C=# S infected S=# susceptibles exposed I = # infectors (# active pulm TB cases) q = # infectious units produced/hr/Infector p = pulm ventilation rate/hr/S t = hours of exposure Q = room ventilation rate with fresh air

  8. Control Measures are Synergistic & Complementary Assumptions: Homogenous distribution of infectious aerosol over 10 hours; uniform susceptibility. - Fennelly KP & Nardell EA. Infect Control Hosp Epidemiol 1998; 19;754

  9. Wells-Riley Mathematical Model of Airborne Infection

  10. TB is Spread by Aerosols, NOT sputum

  11. Particle size & deposition site 100  20  10  – upper airway 1 - 5  – alveolar deposition Time to fall the height of a room 10 sec 4 min 17 min Suspended indefinitely by room air currents Particle size* & suspension in air(* NOT size of bacilli) - Courtesy of Sol Permutt, 2004 *NOT organism size

  12. Six-stage Andersen cascade impactor Andersen AA. J Bacteriol 1958;76:471.

  13. Cough Aerosol Sampling System - Fennelly KP et al. Am J Resp Crit Care Med 2004; 169; 604-9

  14. Cough-generated aerosols of Mtb:Initial Report from Denver, CO4 of 16 (25%) of SS+ subjects - Fennelly KP et al. Am J Resp Crit Care Med 2004; 169; 604-9

  15. Variability of Infectiousness in TB:Epidemiology • Rotterdam, 1967-69: Only 28% of smear positive patients transmitted infections. • Van Geuns et al. Bull Int Union Tuberc 1975; 50:107 • Case control study 796 U.S. TB cases • Index cases tended to infect most (or all) or few (or none) of their contacts • Snider DE et al. Am Rev Respir Dis 1985; 132:125 • Ability to publish outbreaks suggests that they are episodic.

  16. Variability of Infectiousness in TB: Experimental • All infections attributed to 8 of 61 (13%) patients. 50% of infections due to one patient with TB laryngitis. • Riley RL et al. Am Rev Respir Dis 1962; 85:511. • 3 (4%) of 77 patients produced > 73% of the infections in the guinea pigs. • Sultan L. Am Rev Respir Dis 1967; 95:435. • Recent replication of this model in Peru • 118 hospital admissions of 97 HIV-TB coinfected patients • 8.5% caused 98% of secondary GP infections • 90% due to inadequately treated MDR-TB • Escombe AR et al. PLoS Medicine 2008; 5:e188

  17. Occupational TB in Sub-Saharan Africa • Malawi • 25% mortality • Harries AD, Tran R Soc Trop Med Hyg 1999; 93: 32 • Ethiopia • South Africa • Nigeria • 32 of 2,173 HCWs • 15 (47%) as HIV-TB • Salami AK, Nigerian J Clin Prac 2008; 11: 32

  18. What is the magnitude and variability of infectious aerosols of M. tuberculosis?(Can we better identify the most infectious?) Hypothesis 1:Cough-generated aerosols of Mtb can be measured in resource-limited settings. Hypothesis 2:Cough-generated aerosols will be detected in approximately 25-30% of patients with PTB.

  19. Cough Aerosol Sampling Systemv.2

  20. Frequency Distribution of Cough-generated Aerosols of M. tuberculosis and Relation to Sputum Smear Status31/112 (28%) SS+ subjects

  21. Cough-generated Aerosols of M. tuberculosis:Normalized Particle Sizes Lower limit of size range(µ) 7.0 4.7 3.3 2.1 1.1 0.65 Anatomical deposition: Upper airway -- bronchi -- alveoli Abstract, ATS International Conference, 2004.

  22. Pitfalls in Administrative Controls • TB Mortality not prioritized or under surveillance (i.e., no data collection) • HIV screening of HCWs not prioritized • major risk factor for TB disease & death • HAART now feasible in much of world • HIV screening advocated for adm’t patients in US • TB laboratory personnel often not involved in TB infection control efforts • Botswana: 1st AFB smear ‘STAT’ • Decisions re: infectiousness falls onto clinicians with variable expertise

  23. Pitfalls in Environmental Controls • Little or no engineering expertise and support for hospitals & HCFs • No systems of communication / interaction • Different ‘cultures’ and mind-sets • TB nurses or administrators subject to sales pitches from commercial vendors • UVGI lamps in SANTA facilities • Mobile air filters in Newark, NJ • Lack of appreciation of natural ventilation…and its limitations! • Low rate of nosocomial infection in Uganda project • High rate in Tugela Ferry

  24. Pitfalls in Personal Respiratory Protection • Too much attention paid to ‘masks’ at expense of administrative and environmental measures • Rizdon R et al: Renal unit with poor ventilation • Inappropriate use on patients • Focus on fit-testing and regulation rather than on follow up on use in field • Lack of appreciation that not all respirators provide the same level of protection • Need for more protection in high-risk aerosol-inducing procedures, e.g., bronchoscopies

  25. TB-IC Practices for Community Programs • Best administrative control: • Suspect and separate until diagnosed • Surveillance of HCWs with TST (and/or IGRAs) and rapid treatment of LTBI if conversions occur • Best environmental control: Ventilation • Do as much as possible outdoors • Use directional airflow when possible • Natural breeze or fans: HCW ‘upwind’; patient ‘downwind’ • Personal respiratory protection • N95 respirators when indoors or very close (procedures) • Surgical masks on patients to control source

  26. Summary: TB-IC • Administrative controls most important component of TB-IC • ‘Suspect and separate!’ • Prioritize screening HIV in HCWs • Prioritize good ventilation in all areas • Back-up in areas with poor ventilation • Fans, mechanical ventilation, UVGI • Prioritize personal respiratory protection for high risk settings, esp where admin and environ controls limited

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